Electromagnetic radiation medical imaging systems are known in the art. Such systems are generally used to create a representation in the form of an image of the anatomy of a region of interest of a patient. Such electromagnetic radiation medical imaging systems are, for example, X-ray, CT, MRI, US or PET systems.
Medical positioning systems (MPS) are known in the art. Such systems are generally used to track and mark the location of an object (e.g., catheter) in or around the body of a patient. Medical positioning systems may employ electromagnetic radiation to determine the location of a body in a reference coordinate system. More specifically, these systems employ the relationship between the strength of the signal associated with this radiation, as detected by a detector, and the distance of this detector from the source of the radiation. For example, such medical positioning systems may include three electromagnetic radiation transmitters, in the form of transmitting coils, positioned such that the axes normal to the plane crated by one of the turns of each coil are mutually orthogonal. These systems may employ detectors in the form of one or more receiving coils, positioned such that the axes, normal to the plane crated by one of the turns of each coil, are mutually orthogonal. Each coil corresponds to an axis in a reference coordinate frame.
A Medical imaging system may be employed in conjunction with a medical positioning system to obtain the image of the anatomy of a patient and the location of an object within or on the patient. For example, during a catheterization procedure, knowledge of the position of the catheter within the body of a patient, and an image of the anatomy of the region in which the catheterization procedure is performed, may be necessary.
Reference is now made to FIG. 1, which is a schematic illustration of a system, generally referenced 10, for navigating an object, such as a distal tip of a catheter, in conjunction with images of the anatomy of a portion of a body of a patient as, detected by a medical imaging system, which is known in the art. System 10 includes medical imaging system 28, a medical positioning system (MPS) 34, a catheter 16, a display unit 32 and a table 14. Medical imaging system 28 includes an imaging radiation transmitter 30 and an imaging radiation detector 26. Catheter 16 includes a distal end 18. Distal end 18 includes magnetic position radiation detectors (not shown). This position radiation detector may be a single coil detector or a multiple coil detector (not shown). The detector is operative for detecting magnetic fields. Medical positioning system 34 includes positioning radiation transmitters 20, 22 and 24. Positioning radiation transmitters 20, 22 and 24 are, for example, three coils.
Display unit 32 is coupled with imaging radiation detector 26. Positioning radiation transmitters 20, 22 and 24, and catheter 16 are coupled with medical positioning system 34. Catheter 16 is inserted to a patient 12, subjected to a treatment, and navigated towards a region of interest (e.g., the cardiovascular system). Imaging radiation transmitter 30 transmits radiation that passes through patient 12. The radiation, detected by imaging radiation detector 26, is a representation of the anatomy of a region of interest of patient 12. An image representing the anatomy of the region of interest of patient 12 is formed on display unit 32. The image includes catheter 16 and distal end 18. Positioning radiation transmitters 20, 22 and 24 transmit magnetic fields which are mutually orthogonal, corresponding to axes of a reference coordinate frame. The detector at distal end 18 detects the magnetic fields generated by positioning radiation transmitters 20, 22 and 24. The detected signal is related to the position of distal end 18, for example, by the Biot Savart law, know in the art. Thus, the position of distal end 18 is obtained by medical positioning system 34. Positioning radiation transmitters 20, 22 and 24 are located on imaging radiation detector 26 so as to register the coordinate system associated with imaging radiation detector 26 and the coordinate system associated with MPS 34 and to maximize the signal to noise ration of the signals detected by the positioning radiation detector.
However, imaging radiation detector 26 acquires the imaging radiation transmitted by imaging radiation transmitter 30, concurrently with positioning radiation transmitter 20, 22 and 24. Thus, due to the proximity of the positioning radiation transmitters to the imaging radiation detector, the magnetic field generated thereby, may affect imaging radiation detector 26. Consequently the image formed on display unit 32 may be corrupted.
U.S. Pat. No. 6,810,110 to Pelc et al. entitled “X-Ray Tube for Operating in A Magnetic Field” is directed to a method wherein an x-ray source, including a cathode, an anode and magnetic means. The magnetic means produce a magnetic field having magnetic field lines passing from the cathode to the anode to compensate or correct an otherwise undesired magnetic field. The magnetic means may include an electromagnet or permanent magnets. The electromagnet may be electromagnetic windings or coils mechanically coupled to the x-ray source. The permanent magnets may be integrated inside or positioned outside of the x-ray source.
U.S. Pat. No. 6,828,728 to Levinson, entitled “Processing images for removal of artifacts” directs to a method wherein interference in an X-Ray image is removed by processing the image after the acquisition thereof. The method to Levinson, initially identify a region in the image, with a standard deviation below a predetermined threshold. This identified region is declared to be free of artifacts. In the next step, each pixel element, on the outer edges of the imaging sensor, starting from the initially identified region, is cleaned. Cleaning is achieved by testing each pixel in sequence and comparing its value with the two preceding clean neighbours in the respective row or column. If the tested pixel is determined not to have predetermined relationship with respect to these clean neighbours, it is replaced by a pixel value having a predetermined relationship with respect to the clean neighbours. In the last step, the remaining pixels are tested. If a pixel is found not to have a predetermined relationship with its neighbouring pixels, the pixel is replaced with the average value of the neighbouring pixels.
U.S. Pat. No. 6,118,848 to Simon et al. entitled “System and methods for the reduction and elimination of image artifacts in the calibration of X-ray imagers” directs to a method to reduce the representation of calibration markers present in an X-ray image. The representations of the calibration markers are reduced by replacing the pixels representing the calibration markers by pixels related to the pixels surrounding the representation of the calibration markers. The relationship between the surrounding pixels and the replaced pixels may be that of the average of the surrounding pixels or multiple regions averaging.
U.S. Pat. No. 6,314,310 to Ben-Haim et al., entitled “X-Ray Guided Surgical Location System with Extended Mapping Volume”, is directed to a method for displaying anatomical features of interest in the body of a patient acquired by one or more X-ray images, with a probe, inserted into the body of the patient. The probe includes sensing devices such as magnetic field responsive coils for determining six-dimensional position and orientation coordinates. During the surgery, as the probe is advanced into the body of the patient, signals generated by the coils on the probe are used to track the coordinates of the tool and to update accordingly, the display showing the image of the tool and the patient. Preferably, a new X-ray image is acquired from time to time. According to the publication to Ben-Haim et al, a surgeon is able to insert and manipulate the probe in the body of the patient under the visual guidance of an X-ray image of the body that includes continuously-updated representation of the tool. The X-ray images is acquired during the surgical procedure and may be updated as desired.